JPH0848857A - Resin molding - Google Patents

Abstract

PURPOSE:To obtain the subject molding, capable of improving the crack resistance, having high reliability and useful as an electrical insulating material in insulation under a high voltage by filling hollow inorganic particles in a molding resin. CONSTITUTION:This molding is obtained by filling (B) hollow inorganic particles 10 in (A) a molding resin 1 consisting essentially of an epoxy resin. The component (B) is preferably glass beads and the grain diameter thereof is preferably <=50mum. Furthermore, the amount of the filled component (B) is preferably 5-50phr.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a resin molded product.

[0002]

2. Description of the Related Art In heavy electric equipment, resin molded products are
In particular, it is widely used as an electrically insulating material and a structural material for high-voltage insulation. Epoxy resin is a material having excellent moisture resistance, chemical resistance, dimensional stability, electrical characteristics, etc., and is widely used as a material for resin molded parts.

However, the epoxy resin is a very brittle material, and its mechanical strength is remarkably reduced if stress-concentrated portions, minute cracks, foreign matters, defects, voids, etc. are present. There are resin mold parts such as resin insulators that incorporate a fixing metal insert, or resin bushings that incorporate a metal conductor. In this case, a large thermal stress is generated at the resin / metal interface due to the temperature difference between the inside and the outside and the temperature change when the equipment is not in operation, and a crack is easily generated in the epoxy resin having low toughness. Once a crack occurs, it rapidly propagates in the resin without stopping, leading to destruction, and in some cases, causes an accident such as a ground fault.

For example, the characteristics of the vacuum valve are determined by the insulation on the surface. Therefore, as shown in FIG. 10, by wrapping the vacuum valve 2 with the epoxy resin 1 and electrically reinforcing the creepage surface, a very compact insulating structure is obtained. However, the difference in the coefficient of thermal expansion between the alumina forming the valve and the epoxy resin 1 is large, and a large residual stress is generated during the process of cooling from the high temperature during casting to room temperature, or a large thermal stress is generated due to the temperature change during operation suspension. May occur. Also, when holding in cold regions, such as when passing over the polar region by a wheel
It is expected to be cooled to about 35 ° C, and it is exposed to extremely large stress. In such a case, the epoxy resin 1 that wraps the vacuum valve 2 is broken and mechanically and electrically destroyed. Therefore, in addition to directly molding the vacuum valve with an epoxy resin, a two-stage molding method using a buffer layer is applied. This is a method in which the vacuum valve 2 is once wrapped with a soft flexible epoxy resin in a thickness of several mm to form a cushion layer 3, and the outside of the cushion layer 3 is cast again with a hard epoxy resin 1 to finish to a predetermined external dimension. Is. At present, it is inevitable to apply such a two-stage mold to a component such as a vacuum valve that is particularly difficult to mold directly due to its coefficient of thermal expansion and shape.

[0005]

However, in the two-step molding method, the number of complicated steps of depositing the buffer layer with a predetermined thickness is increased. In addition, a new adhesive interface between the buffer layer and the epoxy resin for casting appears, which easily becomes a weak point, and in reality, sufficient characteristics have not yet been obtained in practice.

The most direct effect is to impart toughness, that is, tenacity and crack resistance to the epoxy resin itself. One of the methods to solve this is to disperse the secondary fine particles in the epoxy resin, and it is roughly classified into hard hard particles and soft soft particles.

When the epoxy resin is filled with hard particles such as silica powder or alumina, the particles are well adhered to the resin to be pinned and reinforced and the toughness is improved. This effect is
It increases as the filling amount of hard particles increases. Since the filling of hard particles simultaneously increases the elastic modulus and hardly lowers the static strength, it is applied to actual resin molded products. However, since the viscosity increases and the workability is impaired, the filling amount is limited.

On the other hand, it is known that the toughness is increased even when the epoxy resin is filled with soft fine particles such as rubber and thermoplastic resin. It is considered that this is because when the soft fine particles are present around the minute defect in the epoxy resin which is the starting point of the breakage, the surrounding epoxy resin is easily deformed and the crack tip is blunted. There are two methods for dispersing fine particles of this soft resin in an epoxy resin. The resin may or may not be compatible with the epoxy resin.

For example, CTBN (carb
oxy terminated butadien acrylonitrile copolymer)
Is compatible with the epoxy resin and is completely soluble during mixing with the resin. Furthermore, the epoxy resin undergoes phase separation during the curing process and is dispersed spherically in the epoxy resin. Factors that have a large effect on mechanical properties, such as dispersion density and particle size, are governed by the progress of curing of the epoxy resin, and it is difficult to control this. In particular, in a large-sized resin mold component, it is difficult to cure the entire body at the same time, and a chemical reaction proceeds from a portion to which heat is supplied, such as a die or a metal insert, and the curing proceeds. Therefore, the conditions for the phase separation of CTBN also differ from part to part, and it has been impossible to uniformly disperse CTBN particles of the same shape in the cured molded part. As a result, the variation in characteristics increases,
It has not been put to practical use. Further, when the soft particles have a certain size or more, they act as defects and the static strength is remarkably lowered.

On the other hand, when fine particles of incompatible thermoplastic resin or fine particles of rubber are filled in the epoxy resin, the viscosity remarkably increases and the workability deteriorates sharply, which is not suitable for practical use.

In recent years, a hybrid material in which hard particles and soft particles are simultaneously filled in an epoxy resin has been considered, but the drawbacks in filling soft particles are large and have become a problem. An object of the present invention is to provide a resin mold product having improved crack resistance and high reliability.

[0012]

Means and Actions for Solving the Problems In order to achieve the above object, the present invention is designed to improve the toughness because hollow inorganic particles are filled in a mold resin whose main component is an epoxy resin. You can

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of hollow inorganic particles in an epoxy resin showing an embodiment of the present invention, FIG. 2 is a view for explaining that the hollow inorganic particles of FIG. FIG. 4 is a diagram for explaining the deformation of the resin around the broken particles when a tensile load is applied, and FIG. 4 is a diagram for explaining the blunting of the crack tip in one embodiment of the present invention.

In general, most epoxy resin fractures originate from minute defects, voids, and minute peeling at the interface. As shown in FIG. 11, when a defect such as a crack 4 existing in the epoxy resin 1 or a stress concentration portion is loaded, the epoxy resin is easily broken without being largely deformed.

On the other hand, the hollow inorganic particles 5 as shown in FIG. 1 are filled in the epoxy resin 1. It consists of a thin shell 6 with low mechanical strength. When the hollow inorganic particles 5 are present in a portion where stress is concentrated, such as in the vicinity of a crack, the thin shell 6 is broken as shown in FIG. Shell 6
When is destroyed, the hollow inorganic particles 5 do not act as a rigid body, and thus become particles with low rigidity similar to voids,
Causes stress concentration. That is, as shown in FIG. 3, shear deformation due to stress concentration is induced around the broken particles 7 as the load increases, and plastic deformation 8 occurs in the direction of about 45 ° with respect to the load. When the broken particles 7 approach each other at a certain distance, the plastic deformations 8 are connected to each other, and a large deformation occurs at the crack tip as a whole. As a result, the strain energy of the load is dissipated and the tip of the crack 4 is blunted as shown in FIG. 4, so that fracture is less likely to occur and the toughness is increased.

This mechanism is due to the concentration of stress around the particles and occurs when the elastic modulus of the particles is sufficiently lower than that of the epoxy resin. That is, it may be a void, and the outer shell 6 of the hollow inorganic particle 5 is broken to provide a void. Further, in the portion where the load is low, the shell 6 does not break and acts as a rigid body as it is, so that the overall rigidity does not decrease.

Further, in the case of hollow hard particles, the particles are uniformly dispersed in the resin mold parts, the particle size can be easily controlled, and stable quality can be obtained even for large parts. Furthermore, the viscosity during mixing is slightly increased, and workability is not impaired.

Next, the present embodiment will be specifically described on the basis of experiments by the present inventors. Usually, bisphenol-based solid epoxy resin (eg CY225,
Trade name of Ciba-Geigy is an acid anhydride curing agent (eg H
Modification was performed based on a heat-curable epoxy casting material composed of a combination of Y925, a trade name of Ciba Geigy), and silica powder (for example, Al, a trade name of Tatsumori). The above-mentioned epoxy casting material 9 is filled with hollow inorganic particles 5 (for example, glass beads HSC-110, trade name of Toshiba Ballotini Co., average particle size 10 μm) as shown in FIG. The hollow inorganic particles 5 are present in the epoxy resin 1 together with the silica particles 10. FIG. 6 shows the relationship between the filling amount and the fracture toughness K _IC of the cured material. K _IC increases with the filling of the hollow inorganic particles 5. Especially 5 to 50 ph
The effect is remarkable by filling the range of r (per hundred of resin by weight), and there is an optimal filling range. This range is almost the same regardless of the type of hard particles such as silica powder or the type of epoxy resin.

On the other hand, since the hollow inorganic particles 5 in the epoxy resin 1 are treated as defects, the static strength of the filling system is lowered. It is known that this defect is caused by filling non-adhesive particles having a particle size of a certain size or more. FIG. 7 shows the relationship between the particle size of the glass beads and the bending strength when the glass beads were filled with 30 phr. The bending strength is almost equal to that of the epoxy resin alone when the particle size is 50 μm or less. Therefore, the particle size in terms of static strength
50 μm or less is desirable.

In the case of hard particles, it is possible to freely control the particle size as compared with a phase-separating system such as CTBN, and it is possible to disperse the particles uniformly in the resin mold part. In addition, the viscosity increase during mixing is significantly lower than that of an incompatible system such as a thermoplastic resin, and workability is good.

Since a structural material usually requires a high elastic modulus, it is common to fill a large amount of adhesive hard particles. Also in this case, K _IC can be improved by filling hollow inorganic particles in an amount of 5 to 50 phr and using them together.

Table 1 shows a system in which 200 phr of silane-treated silica powder having good adhesiveness was filled in a heat-curable epoxy casting material composed of the above-mentioned heavy-duty bisphenol solid epoxy resin / acid anhydride curing agent. Shows the mechanical properties of a system filled with 30 phr of hollow glass beads (average particle size 10 μm) and a system filled with 15 phr of soft CTBN.
Table 1 shows that the filling of hollow glass beads is effective for improving the fracture toughness K _IC . The flexural modulus depends on the filling amount of the adhesive particles, so that the filling of the hollow glass beads is good, but the difference is slight, and the bending strength is very small. Further, although the CTBN-filled system is effective in improving the toughness, the bending strength was significantly reduced.

[0023]

[Table 1]

Next, in order to investigate the crack resistance of the same composition, 5 oliphant thermal shock washer methods made of Fe conforming to IEC Pb 455-2 shown in FIG. 8 were cast, and heat treatment was performed under the conditions shown in Table 2. An impact test was conducted.

The test sample is subjected to a heat and cold test at a predetermined temperature for a predetermined time. The temperature range gradually increases as the test progresses. The low temperature is a cooling tank containing ethanol cooled to a desired temperature with dry ice, and the high temperature is obtained by leaving it at room temperature or by a heating furnace. For the judgment, after taking out from the low temperature side, the presence or absence of cracks is visually observed. Table 3 shows the results.

[0026]

[Table 2]

[0027]

[Table 3]

As can be seen from Table 3, the casting material according to the present embodiment filled with the release agent-treated glass beads did not crack even after 17 cycles and had excellent thermal shock resistance. In addition, there were few variations and stable characteristics were obtained.

As the hollow inorganic particles, ceramics can be considered in addition to glass beads, but the same result as that of hollow glass beads can be obtained. Using the resin having the above composition, FIG.
A vacuum valve was directly molded using an epoxy resin filled with a silica powder filling material and hollow glass beads as a molding resin in which the molding valve 9 as described above was cast. In addition, a flexible epoxy resin as a buffer layer
A two-stage molded product was also prepared, which was applied around the vacuum valve in a thickness of 3 mm and then cast with a conventional material.

Using this prototype, boiling water at 100 ℃ and 0 ℃
A liquid phase heat cycle test was conducted by alternately immersing the layers of water in 1 hour each. A visual inspection was performed after 10 cycles of the test. Although cracks were found in the conventional product directly molded, no abnormality was found in the product of this example and the two-stage molded product. Next, a partial discharge test was conducted. When the discharge charge amount at the start of corona generation was set to 10 pC and an alternating current was applied at a pulse generation frequency of 50 pps, the prototype according to this example cleared 20 kV and maintained the initial characteristics. On the other hand, the corona onset voltage by the two-step casting method dropped to 14 kV under the same conditions.

From the above, it was proved that the product of this example is excellent in thermal, mechanical and electrical properties and is highly reliable as compared with the conventional product. In the above examples, 10 to 50 phr of hollow hard particles having a particle size of 50 μm or less are filled and uniformly dispersed in the epoxy resin to increase the toughness and greatly improve the crack resistance. You can

[0032]

As described above, according to the present invention, since the hollow inorganic particles are filled in the mold resin whose main component is the epoxy resin, the mold having high reliability and improved crack resistance is obtained. You can get the goods.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of hollow inorganic particles of a resin molded product showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining a state in which the hollow inorganic particles in FIG. 1 are destroyed by a mechanical load.

FIG. 3 is a diagram for explaining the deformation occurring in the resin around the broken particles when a tensile load is applied in FIG.

FIG. 4 is a view for explaining blunting of a crack tip in one embodiment of the present invention.

FIG. 5 is a cross-sectional view of a heavy-duty epoxy casting material for explaining an embodiment of the present invention.

FIG. 6 is a graph showing the relationship between the filling amount and the fracture toughness K _IC when the hollow glass beads are filled in the epoxy resin for explaining the embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the particle size of hollow glass beads and the bending strength when the epoxy resin is filled with hollow glass beads to explain one embodiment of the present invention.

FIG. 8 is a view showing the shape of an olifant thermal shock washer.

FIG. 9 is a sectional view of a mold valve to which a casting material according to an embodiment of the present invention is applied.

FIG. 10 is a sectional view of a conventional mold valve.

FIG. 11 is a diagram for explaining the occurrence of breakage starting from a minute crack existing in an epoxy resin which is a conventional casting material.

[Explanation of symbols]

1 ... Epoxy resin, 5 ... Hollow inorganic particles, 9 ... Epoxy casting material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaru Miyagawa 1st Toshiba Town, Fuchu City, Tokyo Inside the Toshiba Fuchu factory (72) Inventor Yasufumi Nagata 1-1-1, Shibaura, Minato-ku, Tokyo Toshiba Corporation Head office

Claims (4)

[Claims] 1. A resin molded product, characterized in that hollow inorganic particles are filled in a mold resin whose main component is an epoxy resin. 2. The resin molded product according to claim 1, wherein the hollow inorganic particles are glass beads. 3. The resin mold product according to claim 1, wherein the hollow inorganic particles have a particle diameter of 50 μm or less. 4. The filling amount of the hollow inorganic particles is 5 to 50.
It is phr, The resin molded product in any one of Claims 1-3.